North American Datum. Most current is NAD83 which was adopted by the Canadian Federal Government in 1990, and supersedes the North American Datum of 1927 (NAD27). See Datum.
NAD1927
North American Datum of 1927. The primary local geodetic datum and geographic coordinate system used to map the United States during the middle part of the 20th century, referenced to the Clarke spheroid of 1866 and an initial point at Meades Ranch, Kansas. It is gradually being replaced by the North American Datum of 1983. (Source: ArcGIS dictionary)
NAD1983
North American Datum of 1983. A geocentric datum and graphic coordinate system based on the Geodetic Reference System 1980 ellipsoid (GRS80). Mainly used in North America, its measurements are obtained from both terrestrial and satellite data. (Source: ArcGIS dictionary)
NTDB
The National Topographic Data Base (NTDB) is a digital database developed by Geomatics Canada and enhanced by DMTI Spatial. The NTDB contains extensive map data classified by approximately 850 feature codes and presented by DMTI Spatial in 15 logical cartographic layers. The NTDB is available from DMTI Spatial in standard GIS plug and play formats.
The NTDB conforms to uniform standards and specifications across the country, and includes the features normally found on a topographic map. NTDB maps are available at 1:50,000 and 1:250,000 scale. Major themes covered by the NTDB include:
Address Points
MDU Buildings
Enhanced Points of Interest
Platinum Postal Suite
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